1. Field of the Invention
The present invention relates to an image formation apparatus and method, and more particularly to an image formation apparatus and method which divide the drawing instructions for one page into a plurality of bands and performs image development sequentially, one band at a time.
2. Description of the Related Art
A conventional image formation apparatus of this type, especially a printer capable of printing images in full color, requires a large amount of memory to store therein the drawing instructions and the image data for one page. For this reason, the printer divides a page into a plurality of areas (hereinafter called bands) and sequentially develops the image of the bands to reduce required memory.
Conventionally, the height of a band, set up by a printer driver which divides a page into a plurality of bands for image development processing, is fixed by the memory amount or the number of gradations of a printer, regardless of the amount of drawing data contained in the band. Thus, the development speed depends largely on how dense the drawing data in a band is. In addition, because all bands have the same height, the printer driver designed for use on a color printer requires a monochrome printer to reserve more memory than is actually needed.
To solve this problem, a method of making the height of a band variable is disclosed in Japanese Patent Laid-Open Publication No. Hei 7-195760. That is, when bit-development command data created from code data transferred from the host computer is developed into a bit map for each band, the technology disclosed in Japanese Patent Laid-Open Publication No. Hei 7-195760 analyzes the command data to derive the development time of each band, considers the time required to transfer the video signal of the previously-developed band data as the band development time for the current band, and sets up the band size so that the current band may be developed within that period of time.
However, the method of the prior art analyzes command data to derive the development time of each band, calculates the band development time which is the video signal transfer time of the previously-developed band data, compares the band development time with the video signal transfer time, and sets up the variable band size of each band. This method involves a large amount of processing to determine the band size, increasing the load of band size setup.
It is an object of the present invention to provide an image formation apparatus and method which adjust the height of each of the bands obtained by dividing a page, divide the drawing data for one page into bands for image development and transmission, allow a printer driver and a printer to perform concurrent operations efficiently, increase image development efficiency, prevent a waste of memory, and increase overall print efficiency.
An image formation apparatus according to the present invention comprises a list table storing therein a display list and a drawing position and a drawing area of the display list, the display list being an intermediate object containing information for creating image data recognizable by a printing unit performing printing, the drawing position and the drawing area corresponding to the display list; a display list creating unit receiving drawing instructions, one at a time, to create the display list and, at the same time, storing the drawing position and the drawing area of the display list into the list table; a distributing unit temporarily determining a band area size of each of a plurality of band areas generated by dividing one page after the display lists for one page are created, referencing the list table to calculate a total of drawing areas for the display lists included in the area, determining the band area size such that the total is equal to or smaller than a predetermined threshold, and creating information on the display lists belonging to the band area; an image developing unit developing the display lists belonging to each of the band areas to create the image data; and a transmitting unit transmitting the image data to the printing unit, one band area at a time.
According to this invention, the image formation apparatus temporarily determines the band area size of each of a plurality of band areas of a page, calculates the total of the drawing areas of the display lists for each of the plurality of band areas, and determines the band area size such that the total is equal to or smaller than the predetermined threshold. This simple processing allows the height of each of the bands of the page to be optimally adjusted.
Another image formation apparatus according to the present invention is the image formation apparatus described above, further comprising, a graphic list table for storing therein information on the drawing range of a special graphic requiring a long image-development time, wherein, when the created display list is the display list of the special graphic, the display list creating unit stores information on the drawing range of the display list into the graphic list table, and after the display lists for one page are created, the distributing unit temporarily determines the band area size of each of the plurality of band areas generated by dividing one page, references the graphic list table to check if the special graphic is included in the band area, determines a minimum band area size determined by a coordinate range in which the special graphic is present if the special graphic is included, references the list table to calculate the total of drawing areas of the display lists included in the band area and determines the band area size such that the total is equal to or smaller than a predetermined threshold if the special graphic is not included, and creates information on the display lists belonging to the band area.
The image formation apparatus according to this invention stores into the graphic list table the drawing range information on the display list of a special graphic requiring a long development time and, if the band area includes the special graphic, determines the storage range such that the storage range is the minimum range determined by the coordinate range in which the special graphic is present. Therefore, the image formation apparatus minimizes the size of the band area including the special graphic which requires a long operation time, makes the operation amount well-balanced among the bands, prevents the special graphic from being divided into a plurality of bands, and prevents image development efficiency from being degraded.